In terms of overall gaming performance, the graphical capabilities of the Nvidia GeForce GTX 780M SLI are significantly better than the AMD Radeon R9 M395X 4GB.

The GTX 780M has a 48 MHz higher core clock speed and 128 more Texture Mapping Units than the R9 M395X. This results in the GTX 780M providing 104.9 GTexel/s better texturing performance. This still holds weight but shader performance is generally more relevant, particularly since both of these GPUs support at least DirectX 10.

The GTX 780M has a 48 MHz higher core clock speed and 32 more Render Output Units than the R9 M395X. This results in the GTX 780M providing 26.2 GPixel/s better pixeling performance. However, both GPUs support DirectX 9 or above, and pixeling performance is only really relevant when comparing older cards.

The R9 M395X was released over a year more recently than the GTX 780M, and so the R9 M395X is likely to have better driver support, meaning it will be more optimized for running the latest games when compared to the GTX 780M.

Both GPUs exhibit very powerful performance, so it probably isn't worth upgrading from one to the other, as both are capable of running even the most demanding games at the highest settings.

The GTX 780M has 4096 MB more video memory than the R9 M395X, so is likely to be much better at displaying game textures at higher resolutions. This is supported by the fact that the GTX 780M also has superior memory performance overall.

The GTX 780M has 160 GB/sec greater memory bandwidth than the R9 M395X, which means that the memory performance of the GTX 780M is massively better than the R9 M395X.

The Radeon R9 M395X 4GB has 2048 Shader Processing Units and the GeForce GTX 780M SLI has 3072. However, the actual shader performance of the R9 M395X is 1259 and the actual shader performance of the GTX 780M is 2448. The GTX 780M having 1189 better shader performance and an altogether better performance when taking into account other relevant data means that the GTX 780M delivers a massively smoother and more efficient experience when processing graphical data than the R9 M395X.

The Radeon R9 M395X 4GB requires 125 Watts to run and the GeForce GTX 780M SLI requires 200 Watts. The GTX 780M requires 75 Watts more than the R9 M395X to run. The difference is significant enough that the GTX 780M may have an adverse affect on your yearly electricity bills in comparison to the R9 M395X.